Papermaking machines for removing water from paper material comprise a wire part, a press part and a drier part. The wire part, the press part and the drier part are arranged in the order named along the direction in which a wet paper web is fed.
The press part includes a press comprising a plurality of press mechanisms arranged in series along the direction in which the wet paper web is fed.
In the papermaking machine, the wet paper web is successively transferred to and fed by wet paper web feed belts, which are disposed respectively in the wire part, the press part and the drier part and are made of water absorbing felt. The wet paper web is pressed by the press mechanisms of the press part to squeeze water therefrom, and then is dried in the drier part.
The press mechanisms include a roll press mechanism and a shoe press mechanism. The roll press mechanism is a mechanism having rolls for sandwiching and pressing wet paper web feed belts which hold the wet paper web. The shoe press mechanism is a mechanism having a press roll and a shoe for sandwiching and pressing wet paper web feed belts which hold the wet paper web.
The shoe press mechanism has a pressing section (nipping section) having a greater pressing zone than the roll press mechanism. As a result, the shoe press mechanism is advantageous in that it has a longer pressing time for a better water squeezing capability, and hence has been finding wide use in recent years.
The present applicant has proposed a shoe press belt for use in shoe press mechanisms (Japanese laid-open patent publication No. 2005-307421). The shoe press belt is an endless belt comprising a base layer, a wet paper web-side layer and a shoe-side layer, and is disposed for rotational movement between the press roll and the shoe of the shoe press mechanism.
The shoe press belt disclosed in Japanese laid-open patent publication No. 2005-307421 and other general shoe press belts are disposed between the press roll and the shoe of the shoe press mechanism, and runs in the warpwise direction (MD direction: rotational direction) with the belt having a shoe abutment surface held in contact with the upper surface of the shoe.
The dimension (belt weftwise dimension) of the shoe press belt in the widthwise direction (CMD direction) thereof is greater than the dimension (shoe weftwise dimension) of the shoe in the widthwise direction thereof. The shoe press belt is driven to run by the power transmitted through the wet paper web feed belt as the press roll is actuated. As a result, when the shoe press belt moves through the pressing section, it is subjected to a shearing stress (a type of bending stress).
Consequently, there has been a demand for a technology for preventing the shoe press belt from cracking (particularly cracking in the warpwise direction) due to fatigue even when the shoe press belt undergoes repetitive bending deformation in the pressing section over a long period of time.
Patent document 1: Japanese laid-open patent publication No. 2005-307421
The present invention has been made in efforts to solve the above problems. It is an object of the present invention to provide a belt for a shoe press which has belt portions in predetermined regions corresponding respectively to shoe edges on opposite sides in the widthwise direction of a shoe. The belt portions are partially increased in rigidity to increase the bending stress and crack resistance of the belt for suppressing bending deformations and for preventing the belt from cracking for improved durability.